The proposed investigation is designed to contribute to the understanding of the nature of retinal-opsin interaction in the binding-site of visual pigments and to explore if molecular motion of rhodopsins in their native environment could be correlated to certain pathological states and functional impairments in retinal disorders. Using the technique of affinity labeling it is hoped to identify specific amino acid residues and/or phospholipid components which directly involved in the mechanism of primary events in vision and of the specific absorption characteristics of visual pigments. Anisotropy determinations of delayed fluorescence is proposed as a novel technique of measuring large-scale rotational motion suitable for membrane proteins and aggregates including the visual pigments. Comparative studies of rhodopsins obtained from normal and diseased retinas are planned. If membrane fluidity and its modulation is an important factor for the normal functioning of rhodopsin in vision, it is hoped that such information might provide clues as to the primary biochemical defects which are underlying certain specific degenerative diseases of the retina, f.i. retinitis pigmentosa or other related dystrophies.